Al Gore: "We face a challenge in the conservation of democracy that we must be up to in order to save the climate balance on which our civilization depends."

Christian Aid: "Disease spread by global warming could kill an extra 185 million people in sub-Saharan Africa by the end of the century and turn millions more into refugees unless rich nations take action now."

James Lovelock, climatologist: "The earth has a fever that could boost temperatures by 8 degrees Celsius making large parts of the surface uninhabitable and threatening billions of people's lives ... A hot earth couldn't support much over 500 million."

Chris Thomas, conservation biologist: "By 2050, rising temperatures exacerbated by human-induced belches of carbon dioxide and other greenhouse gases could send more than a million of Earth's land-dwelling plants and animals down the road to extinction."